Abstract
This paper describes a mini-computersystem specifically designed for a surface ionization instrument capable of precise isotopic abundance measurements of uranium and phtonium. The mini-computer system has two major functions; it is possible to reduce the analytical hour and personal errors in measuring the peak height with tools. The system consists of five parts; Analog-Digital-Converter(A. D. C), mini-computer(4 k), teletype, and two mass spectrometers. The data consisted of the A. D. C. voltage level from a vibrating reed electrometer which was connected to the ion beam detector within a mass spectrometer. The voltage level was converted to a digital form by means of a voltage-to-frequency converter(VTFC)and a number of four figure scalers. This out-put was fed into a scdler gated for a predetermined time. The counts in the scaler were then proportional to the voltage level for any given gate time and were read directly into the computer. The gate time for counting the frequency was 0.4 sec and was controlled by the computer. To reduce the measuring error due to noise, the computer calculated the average of three values of before and behind of the actual highest value for the highest value of a peak. When the period between the times measured for the starting value(i. e. the differential value of the frequency of VTFC which changed from zero to plus), and the end value(i. e. the differential value of the frequency of VTFC which changed from minus to zero)of a peak was shorter than the established one, the computer did not detect it as a peak.
